1. Field of the Invention
The present invention relates generally to a multistep preparation of an oligomer oil, and relates more particularly to an aforesaid multistep preparation in which the first step involves the polymerization of a feedstock containing one or more C3 to C20 1-olefins in the presence of a metallocene catalyst system comprising a bulky ligand transition metal catalyst and in which a subsequent step involves the oligomerization of at least a preselected fraction of the product of the first step.
2. Discussion of the Prior Art
Numerous processes have been disclosed for polymerizing or oligomerizing an ethylenically unsaturated olefin. For example, Rossi et al., PCT/US93/12102, published on Jun. 23, 1994 as WO 94/13715, discloses a catalyst system comprising a bulky ligand transition metal compound having a formula which is similar to Formula 1, 2, 3 or 4 herein below. The catalyst system also includes an activator compound containing a metal of Group II or III of the Periodic Table of the Elements, especially trialkyl aluminum compounds, alumoxanes both linear and cyclic, or ionizing ionic activators or compounds such as tri(n-butyl) ammonium tetra(pentafluorophenyl) boron. The disclosed process involves copolymerization of ethylene and an alpha-olefin. Suitable alpha-olefins have one hydrogen atom on the second carbon, at least two hydrogens on the third carbon or at least one hydrogen on the fourth carbon. The resulting copolymers produced contain a high degree of terminal ethenylidene or vinylidene unsaturation, and have a number average molecular weight of 300 to 15,000 and a molecular weight distribution (Mw/Mn) of typically less than 5.
Bagheri et al., U.S. Pat. No. 5,688,887 discloses another such process for polymerizing a feedstock containing one or more C3 to C20 1-olefins and a second hydrocarbon which is not a 1-olefin, to form a highly reactive, low molecular weight, viscous, essentially 1-olefin-containing poly(1-olefin) or copoly(1-olefin) in the presence of a metallocene catalyst comprising a cyclopentadienyl or indenyl Periodic Group IVb metallocene catalyst and aluminoxane cocatalyst. The resulting polymer product has a terminal vinylidene content of more than 80%, is highly reactive and has a molecular weight between 300 and 10,000. Bagheri et al. also discloses reactions of the poly(1-olefin) or copoly(1-olefin) product in which the terminal vinylidene linkage is reacted with an aromatic, an epoxidation agent, a silylation agent, maleic anhydride, carbon monoxide and hydrogen, halogen and hydrohalogen.
A major problem associated with making oligomer oils from vinyl olefins is that the oligomer product mix usually must be fractionated into different portions to obtain oils of a given desired viscosity (e.g., 2, 4, 6 or 8 cSt at 100xc2x0 C.). As a result, in commercial production it is difficult to obtain an oligomer product mix which, when fractionated, will produce the relative amounts of each viscosity product which correspond to market demand, and it is often necessary to produce an excess of one product in order to obtain the needed amount of the other. Another problem is the lack of control over the chemistry, and isomerization of alpha olefins to internal olefins. A third problem is that polymerization processes often yield a high percentage of dimer, which is unsuitable (too volatile) for use as a lubricant. Therefore, it is highly desirable to develop a process that provides the versatility of allowing the viscosity of the product to be tailored with improved selectivity and product oils having a pre-selected desired viscosity to be manufactured reproducibly and easily.
Schaerf et al., U.S. Pat. Nos. 5,284,988 and 5,498,815 disclose two two-step processes for preparing a synthetic oil that do provide improved versatility of allowing one to tailor the viscosity of the synthetic oil product with improved selectivity. U.S. Pat. No. 5,284,988 discloses a process which provides improved selectivity when forming synthetic oils using as starting olefins, vinylidene olefins and alpha-olefins. The process of U.S. Pat. No. 5,284,988 for making a synthetic oil comprises (a) isomerizing at least a portion of a vinylidene olefin feed in the presence of an isomerization catalyst to form an intermediate which contains tri-substituted olefin and (b) codimerizing the intermediate and at least one vinyl olefin in the presence of an oligomerization catalyst to form a synthetic oil which comprises a co-dimer of the vinylidene olefin and the vinyl olefin. Suitable vinylidene olefins for use in the isomerization step of the process of U.S. Pat. No. 5,284,988 can be prepared using known methods such as by dimerizing vinyl olefins containing from 4 to about 30 carbon atoms, preferably at least 6, and most preferably at least 8 to about 20 carbon atoms, including mixtures thereof. Suitable vinyl olefins for use in the codimerization step of the process of U.S. Pat. No. 5,284,988 contain from 4 to about 30 carbon atoms, and, preferably about 6 to about 24 carbon atoms, including mixtures thereof. The codimerization step can use any suitable dimerization catalyst known in the art and especially Friedel-Crafts type catalysts such as acid halides (Lewis Acid) or proton acid (Bronsted Acid) catalysts, which can be used in combination and with promoters.
U.S. Pat. No. 5,498,815 discloses a process for making a synthetic oil which comprises the steps of reacting a vinylidene olefin in the presence of a catalyst to form an intermediate mixture which contains at least about 50 weight percent dimer of the vinylidene olefin, and thereafter adding a vinyl olefin to the intermediate mixture and reacting the intermediate mixture and the vinyl olefin in the presence of a catalyst so as to form a product mixture which contains the dimer of the vinylidene olefin and a co-dimer of the added vinyl olefin with the vinylidene olefin. Suitable vinylidene olefins for use in the first step of this process can be prepared using known methods, such as by dimerizing vinyl olefins containing from 4 to about 30 carbon atoms. Suitable vinyl olefins for use in the second step of this process contain from 4 to about 30 carbon atoms. Both steps can use any suitable dimerization catalyst known in the art and especially Friedel-Crafts type catalysts such as acid halides (Lewis Acid) or proton acid (Bronsted Acid) catalysts, which catalysts can be used in combination and with promoters.
Hobbs et al., PCT/US90/00863, published on Sep. 7, 1990 as WO 90/10050, discloses a method for improving the thermal stability of synthetic lubricants composed of alpha-olefin oligomers by alkylation thereof in the presence of an acid alkylation catalyst with an olefin such as decene or the lower molecular weight, non-lubricant range olefins produced in the course of the oligomerization of 1-alkenes. The alpha-olefin oligomers are obtained by oligomerization of C6 to C20 alpha-olefin feedstock in the presence of a reduced valence state Group VIB metal catalyst on a porous support and recovering from the resulting product mixture oligomers comprising olefinic lubricant range hydrocarbons.
However, neither U.S. Pat. No. 5,284,988, nor U.S. Pat. No. 5,498,815 nor PCT/US90/00863 discloses a multistep process that involves in the first step the polymerization of an olefin in the presence of a metallocene catalyst system comprising a bulky ligand transition metal complex to form a product mixture comprising a distribution of products at least a fraction of which have properties that are outside of a predetermined range therefor, and in a subsequent step the oligomerization of at least a pre-selected fraction of the product mixture formed in the first step.
It is therefore a general object of the present invention to provide an improved process for producing an oligomer oil having predetermined properties which overcomes the aforesaid problems of prior out methods.
More particularly, it is an object of the present invention to provide an improved aforesaid process that permits a greater degree of control over the chemistry and minimizes the degree of double bond-isomerization of the olefins in the feedstock.
It is a related object of the present invention to provide an improved aforesaid process which permits improved efficiency in the conversion of ethylenic olefins to oligomer oils having predetermined properties.
Other objects and advantages will become apparent upon reading the following detailed description and appended claims.
These objects are achieved by the process of the present invention for the selective production of an oligomer oil having predetermined properties comprising a first step (a) of polymerizing a feed comprising one or more C3 to C20 olefins having at least one hydrogen on the 2-carbon atom, at least two hydrogens on the 3-carbon atom and at least one hydrogen on the 4-carbon (if at least 4 carbon atoms are present in the olefin), in the presence of a metallocene catalyst system comprising a bulky ligand transition metal complex of the Formula 1 and an activating quantity of an activator comprising an organoaluminum compound or a hydrocarbylboron compound or a mixture thereof:
LmMXnX1pxe2x80x83xe2x80x83Formula 1
In Formula 1, L is the bulky ligand, M is the transition metal, X and X1 may be the same or different and are independently selected from the group consisting of halogen, hydrocarbyl group or hydrocarboxyl group having 1-20 carbon atoms, m is 1-3, n is 0-3, p is 0-3 and the sum of the integers m+n+p corresponds to the transition metal valency. A product mixture is formed that comprises a distribution of products at least a fraction of which have properties that are outside of a predetermined range therefor. In a subsequent step (b), at least a pre-selected fraction of the product formed in step (a) is oligomerized in the presence of an acidic oligomerization catalyst to thereby form the aforesaid oligomer oil. The resulting product mixture from step (b) contains less than 35 weight percent of oligomers that contain two or less monomeric units and at least 60 weight percent of oligomers that contain three monomeric units.
The metallocene catalyst system employed in step (a) of the method of this invention comprises a bulky ligand transition metal complex of the stoichiometric Formula 1:
LmMXnXipxe2x80x83xe2x80x83Formula 1
wherein L is the bulky ligand, M is the transition metal, X and X1 are independently selected from the group consisting of halogen, hydrocarbyl group or hydrocarboxyl group having 1-20 carbon atoms, and m is 1-3, n is 0-3, p is 0-3, and the sum of the integers m+n+p corresponds to the transition metal valency. The aforesaid metal complex contains a multiplicity of bonded atoms forming a group which may be cyclic with one or more optional heteroatoms. The ligands L and X may be bridged to each other, and if two ligands L and/or X are present, they may be bridged.
The catalyst is a metallocene in which M is a Group IV, V or VI transition metal, and one or more L is a cyclopentadienyl or indenyl moiety. In this embodiment, the feed comprises one or more linear C3 to C20 1-olefins, preferably one or more linear C4 to C20 1-olefins, and the product mixture formed in step (a) comprises an essentially terminally unsaturated viscous, essentially 1-olefin-containing poly(1-olefin) or copoly(1-olefin) of molecular weight between 300 and 10,000 that exhibits a terminal vinylidene content of more than 50%, preferably more than 80%. Preferably, the metallocene is represented by the stoichiometric Formula 2:
(CP)mMR1nR2pxe2x80x83xe2x80x83Formula 2
wherein each Cp is a substituted or unsubstituted cyclopentadienyl or indenyl ring, and each such substituent thereon can be the same or different and is an alkyl, alkenyl, aryl, alkaryl, or aralkyl radical having from 1 to 20 carbon atoms or at least two carbon atoms formed together to form a part of a C4 or C6 ring; wherein R1 and R2 are independently selected from the group consisting of halogen, hydrocarbyl, hydrocarboxyl, each having 1-20 carbon atoms; and wherein m is 1-3, n is 0-3, p is 0-3, and the sum of m+n+p corresponds to the oxidation state of M.
In alternative preferred embodiments, the metallocene is represented by the stoichiometric Formulas 3 or 4:
(C5R3g)kR4s(C5R3g)MQ3xe2x88x92kxe2x88x92xxe2x80x83xe2x80x83Formula 3
or
R4s(C5R3g)2MQ1xe2x80x83xe2x80x83Formula 4
wherein each C5R3g is a substituted or unsubstituted cyclopentadienyl, wherein each R3 may be the same or different and is hydrogen, alkyl, alkenyl, alkaryl or aralkyl having from 1 to 20 carbon atoms or at least 2 carbon atoms joined together to form a part of a C4 to C6 ring; wherein R4 is either 1) an alkylene radical containing from 1 to 4 carbon atoms, or 2) a dialkyl germanium or silicon or an alkyl phosphoric or amine radical, and R4 is substituting on and bridging two C5R3g rings or bridging one C5R3g ring back to M, wherein each Q can be the same or different and is an alkyl, alkenyl, aryl, alkaryl, or arylalkyl radical having from 1 to 20 carbon atoms or halogen, and Qxe2x80x2 is an alkylidene radical having from 1 to 20 carbon atoms; when k is 0, x is 1, otherwise x is always 0; and wherein s is 0 or 1; and when s is 0, g is 5 and k is 0, 1 or 2; and when s is 1, g is 4 and k is 1. M is a transition metal of Group IV, V or VI, preferably Group IV.
Preferably each C5R3g is a monosubstituted cyclopentadienyl of the type C5H4R3 and each R3 may be the same or different and is a primary or secondary alkyl radical. When R3 is a primary alkyl radical, it is preferably methyl, ethyl or n-butyl. When R3 is a secondary radical, it is preferably isopropyl or sec-butyl. The resulting product has a viscosity in the range of 2-20 cSt at 100xc2x0 C. In another preferred embodiment, each C5R3g is a di-, tri-, or tetrasubstituted cyclopentadienyl of the type C5H3R32, C5H2R33 or C5HR34, and each R3 may be the same or different and is a primary or secondary radical. The resulting product has a viscosity of 20-5000 cSt at 100xc2x0 C. In both cases, the reaction is performed at a temperature in the range of from 25 to 150xc2x0 C.
In addition to the bulky ligand transition metal complex, the metallocene catalyst system employed in step (a) of the method of this invention also contains an activating quantity of an activator selected from organoaluminum compounds and hydrocarbylboron compounds. Such organoaluminum compounds include fluoro-organoaluminum compounds. Suitable organoaluminum compounds include compounds of the formula AIR503, where each R50 is independently C1-C12 alkyl or halo. Examples include trimethylaluminium (TMA), triethylaluminium (TEA), tri-isobutylaluminium (TIBA), tri-n-octylaluminium, methylaluminiumdichloride, ethylaluminium dichloride, dimethylaluminium chloride, diethylaluminium chloride, ethylaluminumsesquichloride, methylaluminumsesquichloride, and alumoxanes. Alumoxanes are well known in the art as typically the oligomeric compounds which can be prepared by the controlled addition of water to an alkylaluminium compound, for example trimethylaluminium. Such compounds can be linear, cyclic or mixtures thereof. Commercially available alumoxanes are generally believed to be mixtures of linear and cyclic compounds. The cyclic alumoxanes can be represented by the formula [R51AIO]s and the linear alumoxanes by the formula R52(R53AIO)s wherein s is a number from about 2 to 50, and wherein R51, R52, and R53 represent hydrocarbyl groups, preferably C1 to C6 alkyl groups, for example methyl, ethyl or butyl groups. Alkylalumoxanes such as linear or cyclic methylalumoxanes (MAOS) or mixtures thereof are preferred.
Mixtures of alkylalumoxanes and trialkylaluminium compounds are particularly preferred, such as MAO with TMA or TIBA. In this context it should be noted that the term xe2x80x9calkylalumoxanexe2x80x9d as used in this specification includes alkylalumoxanes available commercially which may contain a proportion, typically about 10 weight percent, but optionally up to 50 weight percent, of the corresponding trialkylaluminium, for instance, commercial MAO usually contains approximately 10 weight percent trimethylaluminium (TMA), while commercial MMAO contains both TMA and TIBA. Quantities of alkylalumoxane quoted herein include such trialkylaluminium impurities, and accordingly quantities of trialkylaluminium compounds quoted herein are considered to comprise compounds of the formula AIR3 additional to any AIR3 compound incorporated within the alkylalumoxane when present.
Examples of suitable hydrocarbylboron compounds are boroxines, trimethylboron, triethylboron, dimethylphenylammoniumtetra(phenyl)borate, trityltetra(phenyl)borate, triphenylboron, dimethylphenylammonium, tetra(pentafluorophenyl)borate, sodium tetrakis[(bis-3,5-trifluoromethyl)phenyl]borate, trityltetra(pentafluorophenyl)borate and tris(pentafluorophenyl) boron.
In the preparation of the catalysts of the present invention, the quantity of activating compound selected from organoaluminium compounds and hydrocarbylboron compounds to be employed is easily determined by simple testing, for example, by the preparation of small test samples which can be used to polymerise small quantities of the monomer(s) and thus to determine the activity of the produced catalyst. It is generally found that the quantity employed is sufficient to provide 0.1 to 20,000 atoms, preferably 1 to 2000 atoms, of aluminum or boron per atom of the transition metal in the compound of Formula 1. Generally, from about 1 mole to about 5000 moles, preferably to about 150 moles of activator are employed per mole of transition metal complex.
When the catalyst system employed in step (a) of the method of this invention comprises a complex of Formulas 5-12, the catalyst preferably comprises a neutral Lewis Base in addition to the bulky ligand transition metal complex and the activator. Neutral Lewis bases are well known in the art of Ziegler-Natta catalyst polymerisation technology. Examples of classes of neutral Lewis bases suitably employed in the present invention are unsaturated hydrocarbons, for example, alkenes (other than 1-olefins) or alkynes, primary, secondary and tertiary amines, amides, phosphoramides, phosphines, phosphites, ethers, thioethers, nitriles, carbonyl compounds, for example, esters, ketones, aldehydes, carbon monoxide and carbon dioxide, sulphoxides, sulphones and boroxines. Although 1-olefins are capable of acting as neutral Lewis bases, for the purposes of the present invention they are regarded as monomer or comonomer 1-olefins and not as neutral Lewis bases per se. However, alkenes which are internal olefins, for example, 2-butene and cyclohexene are regarded as neutral Lewis bases in the present invention. Preferred Lewis bases are tertiary amines and aromatic esters, for example, dimethylaniline, diethylaniline, tributylamine, ethylbenzoate and benzylbenzoate. In this particular embodiment of the present invention, the transition metal complex (first component), activator (second component), and neutral Lewis base (third component) of the catalyst system can be brought together simultaneously or in any desired order. However, if the aforesaid second and third are compounds which interact together strongly, for example, form a stable compound together, it is preferred to bring together either the aforesaid first and second components or aforesaid first and third components in an initial step before introducing the final defined component. Preferably, the first and third components are contacted together before the second component is introduced. The quantities of first and second components employed in the preparation of this catalyst system are suitably as described above in relation to the catalysts of the present invention. The quantity of the neutral Lewis Base (component 3) is preferably such as to provide a ratio of the neutral Lewis Base to the first component of 100:1 to 1:1000, most preferably in the range 10:1 to 1:20. All three components of the catalyst system can be brought together, for example, as the neat materials, as a suspension or solution of the materials in a suitable diluent or solvent (for example a liquid hydrocarbon), or, if at least one of the components is volatile, by utilising the vapour of that component. The components can be brought together at any desired temperature. Mixing the components together at room temperature is generally satisfactory. Heating to higher temperatures, for example, up to 120xc2x0 C., can be carried out if desired, for example, to achieve better mixing of the components. It is preferred to carry out the bringing together of the three components in an inert atmosphere (for example, dry nitrogen) or in vacuo. If it is desired to use the catalyst on a support material (see below), this can be achieved, for example, by preforming the catalyst system comprising the three components and impregnating the support material preferably with a solution thereof, or by introducing to the support material one or more of the components simultaneously or sequentially. If desired, the support material itself can have the properties of a neutral Lewis base and can be employed as, or in place of, the aforesaid third component. An example of a support material having neutral Lewis base properties is poly(aminostyrene) or a copolymer of styrene and aminostyrene (i.e., vinylaniline).
The catalyst employed in the process step (a) of the present invention can be unsupported or supported (absorbed or adsorbed or chemically bound) on a convenient conventional support material. Suitable solid particle supports are typically comprised of polymeric or refractory oxide materials, each being preferably porous, such as for example, talc, inorganic oxides, inorganic chlorides, for example magnesium chloride, and resinous support materials such as polystyrene, polyolefin, or other polymeric compounds or any other organic support material and the like that has an average particle size preferably greater than 10 xcexcm. The preferred support materials are inorganic oxide materials, which include those from the Periodic Table of Elements of Groups 2, 3, 4, 5, 13 or 14 metals or metalloid oxides. In a preferred embodiment, the catalyst support materials include silica, alumina, silica-alumina, and mixtures thereof. Other inorganic oxides that may be employed either alone or in combination with the silica, alumina or silica-alumina are magnesia, titania, zirconia, and the like.
It is preferred that the support material has a surface area in the range of from about 10 to about 700 m2/g, pore volume in the range of from about 0.1 to about 4.0 cc/g and average particle size in the range of from about 10 to about 500 xcexcm. More preferably, the surface area is in the range of from about 50 to about 500 m2/g, the pore volume is in the range of from about 0.5 to about 3.5 cc/g, and the average particle size is in the range of from about 20 to about 200 xcexcm. Most preferably, the surface area range is from about 100 to about 400 m2/g; the pore volume is from about 0.8 to about 3.0 cc/g, and the average particle size is from about 30 to about 100 xcexcm. The pore size of the carrier of the invention typically has pore size in the range of from 10 to about 1000 xc3x85, preferably 50 to about 500 xc3x85, and more preferably 75 to about 350 xc3x85. The bulky ligand transition metal compound is deposited on the support generally at a loading level of 100 to 10 micromoles of transition metal compound to gram of solid support; more preferably from 80 to 20 micromoles of transition metal compound to gram of solid support; and most preferably from 60 to 40 micromoles of transition metal compound to gram of solid support. While the bulky ligand transition metal compound can be deposited on the support at any level up to the pore volume of the support, loading levels of less than 100 micromoles of transition metal compound to gram of solid support are preferred, with less than 80 micromoles of transition metal compound to gram of solid support being more preferred, and less than 60 micromoles of transition metal compound to gram of solid support being most preferred.
Impregnation of the support material can be carried out by conventional techniques, for example, by forming a solution or suspension of the catalyst components in a suitable diluent or solvent, or slurrying the support material therewith. The support material thus impregnated with catalyst can then be separated from the diluent for example, by filtration or evaporation techniques. If desired, the catalysts can be formed in situ in the presence of the support material, or the support material can be pre-impregnated or premixed, simultaneously or sequentially, with one or more of the catalyst components. Formation of the supported catalyst can be achieved, for example, by treating the transition metal compounds of the present invention with alumoxane in a suitable inert diluent, for example, a volatile hydrocarbon, slurrying a particulate support material with the product and evaporating the volatile diluent. The produced supported catalyst is preferably in the form of a free-flowing powder. The quantity of support material employed can vary widely, for example from 100,000 to 1 grams per gram of metal present in the transition metal compound.
The polymerization conditions employed in step (a) of the method of this invention can be, for example, either solution phase, slurry phase, or gas phase and either batch, continuous or semi-continuous, with polymerization temperatures ranging from xe2x88x92100xc2x0 C. to +300xc2x0 C. In the slurry phase process and the gas phase process, the catalyst is generally fed to the polymerization zone in the form of a particulate solid. This solid can be, for example, an undiluted solid catalyst system formed from the bulky ligand transition metal complex employed in the method of the present invention and an activator, or can be the solid complex alone. In the latter situation, the activator can be fed to the polymerization zone, for example as a solution, separately from or together with the solid complex.
In the slurry phase polymerisation process, the solid particles of catalyst, or supported catalyst, are fed to a polymerisation zone either as dry powder or as a slurry in the polymerisation diluent. Preferably, the particles are fed to a polymerisation zone as a suspension in the polymerisation diluent. The polymerisation zone can be, for example, an autoclave or similar reaction vessel, or a continuous loop reactor, e.g. of the type well-known in the manufacture of polyethylene by the Phillips Process.
Methods for operating gas phase polymerisation processes are well known in the art. Such methods generally involve agitating (e.g. by stirring, vibrating or fluidising) a bed of catalyst, or a bed of the target polymer (i.e. polymer having the same or similar physical properties to that which it is desired to make in the polymerisation process) containing a catalyst, and feeding thereto a stream of monomer at least partially in the gaseous phase, under conditions such that at least part of the monomer polymerises in contact with the catalyst bed. The bed is generally cooled by addition of cool gas (e.g. recycled gaseous monomer) and/or volatile liquid (e.g. a volatile inert hydrocarbon, or gaseous monomer which has been condensed to form a liquid). The polymer produced in, and isolated from, gas phase processes forms directly a solid in the polymerisation zone and is free from liquid, or substantially free from liquid. As is well known to those skilled in the art, if any liquid is allowed to enter the polymerisation zone of a gas phase polymerisation process, the quantity of liquid is small in relation to the quantity of polymer present in the polymerisation zone. This is in contrast to xe2x80x9csolution phasexe2x80x9d processes wherein the polymer is formed dissolved in a solvent, and xe2x80x9cslurry phasexe2x80x9d processes wherein the polymer forms as a suspension in a liquid diluent.
Step (a) of the present invention can be operated under batch, semi-batch, or so-called xe2x80x9ccontinuousxe2x80x9d conditions by methods that are well known in the art. The polymerisation process of the step (a) of the method of the present invention is preferably carried out at a temperature above 0xc2x0 C., more preferably above 15xc2x0 C. and most preferably in the range of 25-150xc2x0 C. Adjustment of the polymerisation within these defined temperature ranges can provide a useful means of controlling the average molecular weight of the produced polymer. It is also preferred to conduct step (a) under relatively low hydrogen partial pressures, more preferably less than 100 psi and most preferably less than 50 psi.
Monomers that are suitable for use as the olefin that undergoes reaction in step (a) of the process of the present invention are alpha-olefins which have (1) at least one hydrogen on the 2-carbon atom, (2) at least two hydrogens on the 3-carbon atoms, and (3) at least one hydrogen on the 4-carbon (if at least 4 carbon atoms, are present in the olefin). Preferably such monomers contain from four to twenty carbon atoms. Thus, suitable alpha-olefin monomers include those represented by the formula H2Cxe2x95x90CHR60 wherein R60 is a straight chain or branched chain alkyl radical comprising 1 to 18 carbon atoms and wherein any branching that is present is at one or more carbon atoms that are no closer to the double bond than the 4-carbon atoms. R60 is an alkyl, preferably containing from 1 to 19 carbon atoms, and more preferably from 2 to 13 atoms. Therefore, useful alpha-olefins include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene and mixtures thereof. Preferably the olefin undergoing reaction contains from four to twenty carbon atoms.
Step (a) of the process of the present invention is controlled to make polymer having a number average molecular weight of not greater than 15,000 and typically from 300 to 15,000, and preferably from 400 to 8,000. The number average molecular weight for such polymers can be determined by any convenient known technique. One convenient method for such determination is by size exclusion chromatography (also known as gel permeation chromatography, GPC) which additionally provides molecular weight distribution information (see W. W. Yau, J. J. Kirkland and D. D. Bly, xe2x80x9cModern Size Exclusion Liquid Chromatographyxe2x80x9d, John Wiley and Sons, New York, 1979). The molecular weight distribution (Mw/Mn) of the polymers or copolymers produced in step (a) is typically less than 5, preferably less than 4, more preferably less than 3, e.g., between 1.5 and 2.5.
The polymers produced in step (a) of this invention are further characterized in that up to about 50% or more of the polymer chains possess terminal ethylenylidene-type unsaturation. A minor amount of the polymer chains can contain terminal vinyl unsaturation, that is, POLY-CHxe2x95x90CH2, and a proportion of the polymers can contain internal monounsaturation, for example, POLY-C(Txe2x80x2)xe2x95x90CH(T2), wherein T1 and T2 are each independently an alkyl group containing 1 to 18, preferably to 8 carbon atoms and POLY represents the polymer chain. The polymer products of step (a) of this inventive process comprise chains which can be saturated by hydrogen, but preferably contain polymer chains wherein at least 50, preferably at least 60, and more preferably at least 75 percent (e.g. 75-98%), of which exhibit terminal ethenylidene (vinylidene) unsaturation. The percentage of polymer chains exhibiting terminal ethenylidene unsaturation may be determined by Fourier Transform Infrared (FTIR) spectroscopic analysis, titration, proton (H)NMR, or C13NMR.
In one preferred embodiment, step (a) is conducted under solution phase conditions using a catalyst system comprising a catalyst of Formula 2, 3 or 4, in which M is a Group IVb transition metal, typically titanium, zirconium or hafnium, and aluminoxane as an activator with the molar ratio of aluminoxane to metallocene of 150 or greater, and C3-C20 alpha-olefins in a feedstock containing more than 1 weight percent of at least one volatile hydrocarbon liquid but consisting essentially of the C3-C20 alpha-olefins, are polymerized to form an essentially terminally-unsaturated, viscous, essentially-1-olefin-containing poly(1-olefin) or copoly(1-olefin), having a terminal vinylidene content of more than 50%.
In this preferred embodiment, the terminally unsaturated, viscous polymer product of this invention is essentially a poly(1-olefin) or copoly(1-olefin). The polymer chains of the viscous polymers produced in step (a) of the method of this invention are essentially terminally-unsaturated. By essentially terminally-unsaturated is meant that preferably more than about 90% of the polymer chains contain unsaturation, more preferably more than about 95% of the polymer chains in the product polymer contain terminal unsaturation.
In general, the products produced in step (a) are mixtures whose components and their relative amounts depend upon the particular alpha-olefin reactant, the catalyst and reaction conditions employed. Typically, the products are unsaturated and have viscosities ranging from about 2 to about 5000 cSt at 100xc2x0 C. At least a portion of the product mixture generally has the desired properties, for example, viscosity, for a particular application. The components in such portion are usually hydrogenated to improve their oxidation resistance and are known for their superior properties of long-life, low volatility, low pour points and high viscosity indices, which make them a premier basestock for state-of-the-art lubricants and hydraulic fluids.
However, usually such product mixture includes substantial amounts of unreacted olefin feed as well as product components which do not have the desired properties or do not include the relative amounts of each viscosity product which correspond to market demand. Thus, step (a) is often performed under conditions that are necessary to produce a product mixture that contains an undesired excess or inadequate amount of one product in order to obtain the desired amount of another product.
The process of the present invention solves this problem by fractionating the product mixture produced in step (a) in order to separate and recover one or more fraction, containing the components having the desired properties and separating one or more other fraction of the product mixture for additional processing in step (b) of the method of this invention. In a less preferred alternative, the entire product from step (a) can be oligomerized in step (b).
The fraction(s) selected for additional processing is then subjected to oligomerization conditions in contact with an oligomerization catalyst in step (b) such that a product mixture containing at least one product having desired properties and in a desired amount that is not produced in step (a). Typically, the low molecular weight fraction, preferably comprising the monomeric and dimeric components thereof, of the product of step (a) is separated and oligomerized in step (b). In three alternative preferred embodiments, in one case, the monomeric and dimeric components of the product of step (a), in a second case, the dimeric components of the product of step (a) and in a third case, the dimeric and a portion of the trimeric components (with or without monomeric components) of the product of step (a) are separated and oligomerized in step (b). Thus, step (b) permits the olefin feed to step (a) to be converted with greater efficiency to desired amounts of products having desired properties. Thus, the method of the present invention permits improved control of the makeup of the feed and permits a wide range of customer specific oligomer oil products to be produced.
For example, the higher molecular weight portion of the product of step (a) has advantageous properties when compared to products that are currently in the marketplace. To illustrate, when 1-decene is employed as the feedstock to step (a), the higher molecular weight portion of the product of step (a) is primarily C30+ has advantages relative to a polyalphaolefin having a viscosity of 6 cSt or higher because it has a higher viscosity index than the polyalphaolefin having a comparable viscosity. For example, in Example 1 hereinbelow the fraction of the product of step (a) has a viscosity of 9.5 cSt at 100xc2x0 C., and a viscosity index of 161 by comparison to the current commercially available polyalphaolefin having a viscosity of 9.4-10 cSt at 100xc2x0 C. and a viscosity index of only 137. Similarly, in Example 3 hereinbelow, the higher molecular weight distillation bottoms fraction has a viscosity of 6 cSt at 100xc2x0 C. and a viscosity index of 153 by comparison to the current commercially available polyalphaolefin having a viscosity of 5.8-6.0 cSt at 100xc2x0 C. and a viscosity index of 135. Furthermore, when step (a) of Example 1 is performed at a temperature of 40xc2x0 C., the higher molecular weight distillation bottoms fraction of the product of step (a) has a viscosity of about 40 cSt at 100xc2x0 C. and a viscosity index of 180 by comparison to the current commercially available polyalphaolefin having a viscosity of 40 cSt at 100xc2x0 C. and a viscosity index of 151.
However, the remaining lower molecular weight portion of the product step (a) is a relatively large volume of low value and lighter oligomeric (primarily dimer and unreacted monomer) fraction. The method of this invention serves to upgrade this lower molecular weight portion of the product of step (a), which is separated from the aforesaid higher molecular weight portion by any convenient conventional means, for example, distillation, and is then upgraded in step (b). For example, when 1-decene is employed as the feedstock to step (a) and when the portion of the product of step (a) containing 20 carbon atoms and less is employed as the feed or portion of the feed to step (b), this low molecular weight portion from step (a) is converted in step (b) to a product mixture in which at least 60%, preferably over 70%, and most preferably over 80% of this crude product mixture contains greater than 24 carbon atoms, preferably greater than 27 carbon atoms, and most preferably greater than 29 carbon atoms. The product mixture of step (b) also contains at most 25%, and preferably not more than 15% of carbon numbers greater than C48; preferably the product mixture of step (b) contains less than 25%, and more preferably less than 15% of carbon numbers greater than C38. The product of step (b) has sufficiently low volatility, a sufficiently high viscosity index, a desirable viscosity in the range of 4 to 5.5 cSt at 100xc2x0 C. and less than 5500 cSt at xe2x88x9240xc2x0 C., and a sufficiently low pour point to serve as base fluids or portions of base fluids for 0W- and 5W-passenger car motor oils and heavy-duty diesel oils. Generally, engine oil formulations and, more particularly 0-W and 5-W engine oil formulations, that comprise at least the fraction of the product mixture of step (b), at least 60 weight percent of which are oligomers that contain three monomeric units (as defined below), are especially advantageous.
Any suitable oligomerization catalyst known in the art, especially an acidic oligomerization catalyst system, and especially Friedel-Crafts type catalysts such as acid halides (Lewis Acid) or proton acid (Bronsted Acid) catalysts can be employed as the oligomerization catalyst of step (b). Examples of such oligomerization catalysts include but are not limited to BF3, BCl3, BBr3, sulfuric acid, anhydrous HF, phosphoric acid, polyphosphoric acid, perchloric acid, fluorosulfuric acid, aromatic sulfuric acids, and the like. Like the catalyst employed in step (a), the oligomerization catalyst can be unsupported or supported (absorbed or adsorbed or chemically bound) on a convenient conventional support material. Preferably the oligomerization catalyst is supported. Suitable support materials and their characteristics and impregnation techniques are discussed hereinabove with respect to the catalyst employed in step (a).
Such oligomerization catalysts can be used in combination and with promoters such as water, alcohols, hydrogen halide, alkyl halides and the like. A preferred catalyst system for the oligomerization process of step (b) is the BF3-promoter catalyst system. Suitable promoters are polar compounds and preferably alcohols containing about 1 to 10 carbon atoms such as methanol, ethanol, isopropanol, n-propanol, n-butanol, isobutanol, n-hexanol, n-octanol and the like. Other suitable promoters include, for example, water, phosphoric acid, fatty acids (e.g., valeric acid) aldehydes, acid anhydrides, ketones, organic esters, ethers, polyhydric alcohols, phenols, ether alcohols and the like. The ethers, esters, acid anhydrides, ketones and aldehydes provide good promotion properties when combined with other promoters which have an active proton e.g. water or alcohols.
Amounts of promoter are used which are effective to provide good conversions in a reasonable time. Generally, amounts of 0.01 weight percent or greater, based on the total amounts of olefin reactants, can be used. Amounts greater than 1.0 weight percent can be used but are not usually necessary. Preferred amounts range from about 0.025 to 0.5 weight percent of the total amount of olefin reactants. Amounts of BF3 are used to provide molar ratios of BF3 to promoter of from about 0.1 to 10:1 and preferably greater than about 1:1. For example, amounts of BF3 of from about 0.1 to 3.0 weight percent of the total amount of olefin reactants are employed.
The amount of catalyst used can be kept to a minimum by bubbling BF3 into an agitated mixture of the olefin reactant only until an xe2x80x9cobservablexe2x80x9d condition is satisfied, i.e. a 2xc2x0-4xc2x0 C. increase in temperature. Because the vinylidene olefins are more reactive than vinyl olefin, less BF3 catalyst is needed compared to the vinyl olefin oligomerization process normally used to produce PAO""s.
The high degree of vinylidine type unsaturation of the product of step (a) when catalysts of Formula 2, 3, or 4 are used makes the product very reactive in the oligomerization of step (b). In addition, since either the entire amount of product of step (a) or one or more preselected fractions of it can be oligomerized in step (b), it is possible in the method of this invention to tailor the feedstock to step (b) in order to produce the desired relative amounts of each viscosity product desired without producing an excess of one product in order to obtain the desired amount of another product which is desired.
A further embodiment of the method of this invention is to co-oligomerize in step (b) a pre-selected fraction of the product of step (a) with at least one vinyl olefin containing 4 to 20 carbon atoms. This allows for conversion of a fraction of the product of step (a) which may not be useful, for example, the dimer fraction, to a higher fraction, for example, a trimer fraction, which is useful. The addition of a different vinyl olefin than used in step (a) to the feed of step (b) permits further control of the make-up of the feed to step (b), and an even wider range of customer specific oligomer oils to be produced. It also allows for production of an oligomer fraction which could not easily be made from other means, for example, co-oligomerizing the C20 polymer from step (a) with C12 vinyl olefin in step (b) to form primarily a C32 product. In addition, the distribution of products is highly peaked in favor of oligomers having three monomeric units and requires minimal fractionation. The identity of the vinyl olefin employed and the relative amounts of vinyl olefin and aforesaid fraction of the product mixture of step (a) in step (b) can be varied to control the amount of products formed in step (b).
Suitable vinyl olefins for use as additional compounds to be added to the feed to step (b) in the process contain from 4 to about 30 carbon atoms, and, preferably, about 6 to 20 carbon atoms, including mixtures thereof. Non-limiting examples include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene and the like. Pure vinyl olefins or a mixture of vinyl olefins and vinylidene and/or internal olefins can be used. Usually, the feed contains at least about 85 weight percent vinyl olefin. Additionally, step (b) can be run so that only a fraction of the vinyl olefin reacts with the preselected polymer fraction from step (a).
The oligomerization of step (b) is very specific for the formation of an oligomer containing three monomeric units. The product mixture formed in step (b) contains less than 35%, preferably less than 25%, more preferably less than 15% by weight of oligomers that contain two or less monomeric units. The product mixture formed in step (b) also contains at least 65%, preferably at least 75%, more preferably at least 85% by weight of oligomers that contain three or more monomeric by weight units, and less than 20%, preferably less than 15% more preferably less than 10% of four or more monomeric units. Thus, the product mixture formed in step (b) generally contains at least 60%, preferably at least 65%, more preferably at least 70%, and most preferably at least 80% by weight of oligomers having three monomeric units.
As employed in this context, the term xe2x80x9cmonomeric unitsxe2x80x9d is intended to mean both (i) the monomer(s) employed in the feed to step (a) and (ii) the monomer(s) added in step (b) to the portion of the product from step (a) that is employed as the feed to step (b). Each such monomer can be the source of one or more of the monomeric units that make up an oligomer in the product produced in step (b). Thus, if no additional vinyl olefinic monomer is added to the portion of the product from step (a) that is employed in the feed to step (b), the monomers employed in the feed to step (a) are the source of all of the monomeric units in the products formed in step (b). However, if one or more vinyl olefinic monomers are added to the portion of the product from step (a) that is employed in the feed to step (b), both (i) such monomers added in step (b) and (ii) the monomers employed in the feed to step (a) are sources of the monomeric units in the products formed instep (b).
For example, if 1-decene is the feed to step (a) and no other vinyl monomer is added to the feed to step (b), the oligomers formed in step (b) and having three monomeric units are trimers of 1-decene. However, if 1-decene is employed as the feed to step (a) and 1-dodecene is added to the feed to step (b), then the oligomers formed in step (b) and having three monomeric units have 30, 32, 34 or 36 carbon atoms, with the relative amounts of each depending upon the relative amount of 1-dodecene added.
By varying the choice of the fraction of the product of step (a) that is employed in the feed to step (b) and of the vinyl olefin added in step (b), customer-specific oligomer oil products can be produced. For example, the viscosity of such a product can be varied by changing the amount and type of vinyl olefin added to the reaction mixture for the second step. A range of molar ratios of aforesaid pre-selected fraction of the product of step (a) to the vinyl olefin added can be varied, but usually at least a molar equivalent amount of vinyl olefin to the dimeric portion of the aforesaid pre-selected fraction of the product of step (a) is used in order to consume the dimeric portions of the aforesaid pre-selected fraction of the product of step (a). The product oils have viscosities of from about 1 to 20 cSt at 100xc2x0 C. Preferably, mole ratios of from about 10:1 to 1:1.5 and most typically about 1.3:1 of the added vinyl olefin to the aforesaid pre-selected fraction of the product of step (a) are used for the feed to step (b). The vinyl olefin is typically added at a time when at least about 30 percent by weight of the aforesaid pre-selected fraction of the product of step (a) has been oligomerized in step (b).
Step (b) can be carried out at atmospheric pressure. Moderately elevated pressures, e.g. to 50 pounds per square inch, can be used and may be desirable to minimize reaction time but are not necessary because of the high reactivity of the vinylidene olefin. Reaction times and temperatures in step (b) are chosen to efficiently obtain good conversions to the desired product. Generally, temperatures of from about 0xc2x0 to 70xc2x0 C. are used with total reaction times of from about 15 minutes to 5 hours.
The products from step (b) of the method of the present invention do have the pre-selected desired properties, especially viscosity. Typically, the products of step (b) are characterized, following removal of unreacted monomer and dimer, by having a viscosity between 3 and 100 cSt, a viscosity index between 110 and 180, a pour pt less than xe2x88x9230xc2x0 C., and a Noack volatility at 250xc2x0 C. between 2% and 25%.
The following examples will serve to illustrate certain specific embodiments of the invention disclosed herein. These examples are for illustrative purposes only and should not be construed as limiting the scope of the novel invention disclosed herein as there are many alternative modifications and variations which will be apparent to those skilled in the art and which fall within the scope and spirit of the disclosed invention.